Joseph de Rooij and Keetje Waas married in 1905 in Amsterdam. They had five children, among whom Elisabeth and the here mentioned Saartje and Anna.
Stadsarchief Amsterdam, archiefkaart Joseph de Rooij
In addition, a Jokos file (number 3514) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.